The purpose of this study is to improve the ability to diagnose problems after mild traumatic brain injury (MTBI) and to test a drug that may improve the outcome from these injuries. Of the more than 1.5 million people who experience a traumatic brain injury (TBI) each year in the United States, as many as 75% sustain a mild TBI which can cause long-term or permanent impairments/disabilities in a significant proportion of patients. In addition, traumatic brain injury has become a signature injury of the wars in Iraq and Afghanistan. For people with these injuries, it is difficult to determine whether symptoms are due to the head injury or another condition, such as Post-traumatic Stress Disorder. In this project, there are 3 observational studies that involve testing of mental functions and behavior, imaging of the brain with special x-ray procedures, and blood samples to look at glandular function, which may be affected by head injury. A fourth study is a test of a drug, atorvastatin, which may provide protection for injured brain cells and improve outcome. By collecting and analyzing the information from these tests, it will be possible to make the process of diagnosing mild TBI or post traumatic stress disorder (PTSD) more precise, and also to see if atorvastatin is a helpful drug for patients with MTBI.